Electronic camera capable of having results of previous image pickup processing reflected in current image pickup processing

ABSTRACT

An electronic camera according to the present invention includes an imaging part, a conditional information determining part, a storage part and a correction processing part. The imaging part images a subject to produce image data. The conditional information determining part determines conditional information that is indicative of the conditions of the subject at a time when the subject is imaged. The storage part stores previous conditional information determined by the conditional information determining part. The correction processing part performs correction processings on the image data, according to both the previous conditional information stored in the storage part and the latest conditional information determined by the conditional information determining part. This enables results of the previous correction processings to be reflected in the current processing, thereby realizing the correction processing with both adaptability and stability.

CROSS REFERENCE TO RELATED APPLICATION

[0001] The disclosure of the following priority application is hereinincorporated by reference: Japanese Patent Application No. 2002-025712,filed Feb. 1, 2002.

BACKGROUND OF THE INVENTION

[0002] 1.Field of the Invention

[0003] The present invention relates to electronic cameras that performimage pickup processings, specifically, correction processings on imagedata, and exposure control at the time of photographing.

[0004] 2. Description of the Related Art

[0005] A typical electronic camera performs a variety of correctionprocessings such as white balance adjustment, gray level correction,color correction on image data outputted from the image sensor, in orderto obtain an image adapted to the various conditions of a subject (forexample, a light source illuminating the subject, contrast and so on),Some conventional electronic camera includes a color temperaturedetermining part that determines the color temperature of a light sourceilluminating a subject. Such electronic camera achieves a white balanceadjustment (in some instances, color correction) using the determinedcolor temperature as a control parameter.

[0006] Also, another conventional electronic camera includes a contrastdetermining part that determines the contrast of a subject, andimplements a gray level correction using the determined contrast as acontrol parameter.

[0007] These electronic cameras determine the latest color temperatureand contrast of an image at the time when the release button is presseddown or immediately before that. Conventionally, the correctionprocessings are implemented according to the latest color temperatureand contrast. In such a case, when conditions of a subject vary duringcontinuous shooting, the correction processings are performed inaccordance with the variations of the subject.

[0008] However, there is a case where the position of the subject shiftseven during the continuous shooting of the same subject, resulting incausing the color temperature determined by the electronic camera tovary. This causes a problem that the white balance of the same subjectvaries among a plurality of images. If these images are sequentiallyreproduced, the user may feel the images very unnatural.

[0009] Especially, a subject having a red color is very susceptible tothe white balance adjustment. Therefore, the above problem issignificant when a red moving car, for example, is continuously shotwithin an angle of field. Similar problems occur not only in performingthe white balance adjustment but also in the gray level correction andcolor correction.

[0010] In order to obtain stable results of the correction processings,some conventional methods have been contrived which limits the variationvalues of control parameters within a predetermined range.

[0011] However, such methods are disadvantageous in that when theconditions of a subject distinctively change, for example, when a car ismoving from a sunny place to a shady place or vise versa, it is veryhard to perform the correction processings in accordance with suchvariations.

[0012] Some electronic cameras each perform exposure controls (includinggain adjustment to analog image signals) with a high adaptability, basedon the brightness repetitively determined by a photometric sensor or thelike. Such electronic cameras, however, disadvantageously performexposure control in accordance with such a variation even in the casewhere the conditions of a subject temporarily vary irrespective of theuser's intention during a course of his/her continuous shooting of thesame subject.

[0013] As explained above, there have been unsolved problems in theconventional image pickup processings (particularly, correctionprocessings and exposure controls) that enhancing the stability of theprocessings will degrade adaptability thereof, while enhancing theadaptability will degrade the stability.

SUMMARY OF THE INVENTION

[0014] In order to solve the above-described problems, it is an objectof the present invention to provide an electronic camera capable ofperforming the image pickup processings with both stability andadaptability at the same time.

[0015] The present invention will now be described below.

[0016] (1) An electronic camera according to the present inventionincludes an imaging part, a conditional information determining part, astorage part and a correction processing part. The imaging part images asubject to produce image data. The conditional information determiningpart determines conditional information that is indicative of theconditions of the subject at the time when the imaging part images thesubject. The storage part stores previous conditional informationdetermined by the conditional information determining part. Thecorrection processing part performs correction processing on the imagedata, based on both the previous conditional information stored in thestorage part and current conditional information determined by theconditional information determining part.

[0017] (2) More preferably, the conditional information determining partdetermines at least color temperature as the conditional informationwhen the correction processing part performs a white balance adjustmentor a color correction.

[0018] Also preferably, the conditional information determining partdetermines at least contrast as the conditional information when thecorrection processing part performs a gray level correction.

[0019] Also preferably, the conditional information determining partproduces color information quantitatively indicative of a major colorwithin an angle of field, when the correction processing part performs acolor correction.

[0020] (3) More preferably, the correction processing part has a controlparameter calculating part that calculates a control parameter, which isused for the correction processings on the image data each time theimaging part produces the image data. The storage part stores theprevious control parameter calculated by the control parametercalculating part. The control parameter calculating part calculates anew control parameter in accordance with a difference between theprevious and current conditional information by combining the previouscontrol parameter stored in the storage part with the control parameterobtained based on the current conditional information.

[0021] (4) More preferably, the conditional information includes thebrightness of the subject. In such case, when the variation amount ofthe brightness is equal to or greater than an upper limit value, thecontrol parameter calculating part determines, as the new controlparameter, the control parameter obtained based on the currentconditional information. When the variation amount of the brightness isless than a lower limit value, the control parameter calculating partdetermines the previous control parameter as the new control parameter.

[0022] (5) More preferably, the electronic camera according to thepresent invention further includes an image pickup time obtaining partfor obtaining image pickup time each time the imaging part produces theimage data. The correction processing part has a control parametercalculating part that calculates a control parameter, which is used forthe correction processings on the image data each time the imaging partproduces the image data. The storage part stores the previous controlparameters calculated by the control parameter calculating part.

[0023] In such case, when an elapsed length of time from the previousimage pickup to the present image pickup is equal to or greater than anupper limit value, the control parameter calculating part determines, asthe new control parameter, the control parameter obtained based on thecurrent conditional information.

[0024] When the elapsed length of time is less than a lower limit value,the control parameter calculating part determines the previous controlparameter stored in the storage part as the new control parameter.

[0025] (6) More preferably, the electronic camera according to thepresent invention has an electric flash for emitting light built in ormounted thereon as an accessory. The correction processing part has acontrol parameter calculating part that calculates a control parameter,which is used for the correction processings on the image data, eachtime the imaging part produces the image data. The storage part storesthe previous control parameters calculated by the control parametercalculating part.

[0026] In the case where presence to absence of the emission from theelectric flash changes between the previous image pickup and the presentimage pickup, the control parameter calculating part determines, as thenew control parameter, the control parameter obtained based on thecurrent conditional information.

[0027] When presence to absence of the emission from the electric flashdoes not change between the previous image pickup and the present imagepickup, the control parameter calculating part determines the previouscontrol parameters stored in the storage part as the new controlparameter.

[0028] (7) More preferably, the control parameter calculating partinitializes the previous control parameter and the value of previousconditional information stored in the storage part-when presence toabsence of the emission from the electric flash changes between theprevious image pickup and the present image pickup.

[0029] (8) Another electronic camera according to the present inventionincludes an imaging part, a conditional information determining part, astorage part, a control parameter calculating part and an exposurecontrol part as follows.

[0030] The imaging part images a subject to produce image data. Theconditional information determining part repetitively determinesconditional information indicative of the conditions of the subject. Thestorage part stores previous conditional information determined by theconditional information determining part. The control parametercalculating part repetitively calculates, based on both the previousconditional information stored in the storage part and currentconditional information determined by the conditional informationdetermining part, the control parameter to be used for an exposurecontrol at the time when the imaging part produces the image data. Theexposure control part performs the exposure control by use of thecontrol parameter calculated immediately before the imaging partproduces the image data.

[0031] (9) Another electronic camera according to the present inventionincludes an imaging part, a conditional information determining part, astorage part, a control parameter calculating part and a correctionprocessing part as follows.

[0032] The imaging part images a subject to produce image data. Theconditional information determining part repetitively determinesconditional information indicative of the conditions of the subject. Thestorage part stores previous conditional information determined by theconditional information determining part. The control parametercalculating part repetitively calculates, based on both the previousconditional information stored in the storage part and currentconditional information determined by the conditional informationdetermining part, the control parameter to be used for correctionprocessings on the image data produced by the imaging part. Thecorrection processing part performs the correction processings by use ofthe control parameter calculated immediately before the imaging partproduces the image data.

[0033] (10) More preferably, the conditional information determiningpart determines at least color temperature as the conditionalinformation when the correction processing part performs a white balanceadjustment or a color correction.

[0034] Also preferably, the conditional information determining partdetermines at least contrast as the conditional information when thecorrection processing part performs a gray level correction.

[0035] Also preferably, the conditional information determining partgenerates color information quantitatively indicative of a major colorwithin an angle of field, when the correction processing part performs acolor correction.

[0036] (11) More preferably, the storage part stores the previouscontrol parameter calculated by the control parameter calculating part.In this case, the control parameter calculating part calculates a newcontrol parameter in accordance with a difference between the previousand current conditional information by combining the previous controlparameter stored in the storage part with the control parameter obtainedbased on the current conditional information.

[0037] (12) More preferably, the conditional information includes thebrightness of the subject. When the variation amount of the brightnessis equal to or greater than an upper limit value, the control parametercalculating part determines, as the new control parameter, the controlparameter obtained based on the current conditional information.

[0038] When the variation amount of the brightness is less than a lowerlimit value, the control parameter calculating part determines theprevious control parameter as the new control parameter.

[0039] (13) More preferably, the electronic camera according to thepresent invention includes an image pickup time obtaining part forobtaining image pickup time each time the imaging part produces imagedata. The storage part stores the previous control parameter calculatedby the control parameter calculating part.

[0040] When an elapsed length of time from the previous image pickup tothe present image pickup is equal to or greater than an upper limitvalue, the control parameter calculating part determines, as the newcontrol parameter, the control parameter obtained based on the currentconditional information.

[0041] When the elapsed length of time is less than a lower limit value,the control parameter calculating part determines the previous controlparameter stored in the storage part as the new control parameter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The nature, principle, and utility of the invention will becomemore apparent from the following detailed description when read inconjunction with the accompanying drawings in which like parts aredesignated by identical reference numbers, in which:

[0043]FIG. 1 is a block diagram showing the functions of an electroniccamera of a first embodiment according to the present invention;

[0044]FIG. 2 is a flowchart showing the operation of a control parametercalculating part in the first embodiment;

[0045]FIG. 3 is a diagram showing an example of an LUT referred to whenthe color temperature weighting rate is decided;

[0046]FIG. 4 is a diagram showing an example of an LUT referred to whenthe contrast weighting rate is decided;

[0047]FIG. 5 is a diagram showing an example of an LUT referred to whenthe color information weighting rate is decided;

[0048]FIG. 6 is a flowchart showing the operation of a control parametercalculating part in a second embodiment; and

[0049]FIG. 7 is a diagram showing an example of an LUT referred to whenthe brightness weighting rate is decided.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] Embodiments of the present invention will be described below indetail with reference to the drawings.

FIRST EMBODIMENT

[0051]FIG. 1 is a block diagram showing the functions of a firstembodiment of the present invention. In FIG. 1, an electronic camera 1includes constituent elements as follows:

[0052] (1) an image pickup part 11 that includes a shooting opticalsystem, a diaphragm, an image sensor and so on and produces image dataof a subject;

[0053] (2) an A/D converting part 12 that digitalizes the image dataproduced by the image pickup part 11;

[0054] (3) an image data processing part 13 that performs a variety ofcorrection processings such as white balance adjustment, gray levelcorrection, color correction on the digitalized image data;

[0055] (4) a recording part 14 that compresses the image data subjectedto the foregoing variety of correction processings to record them on apredetermined recording medium;

[0056] (5) a color temperature determining part 15 that determines colortemperature.

[0057] (6) a contrast determining part 16 that determines contrast;

[0058] (7) a color detecting part 17 that generates color informationquantitatively indicative of major colors within an angle of field;

[0059] (8) a photometric sensor 18 that determines brightness;

[0060] (9) an electric flash 19 that emits light to illuminate asubject; and

[0061] (10) a timer 20 that clocks image pickup time and so on.

[0062] The foregoing image data processing part 13 includes constituentelements as follows:

[0063] (11) a control parameter calculating part 30 that calculatescontrol parameters for deciding the degrees of the correctionprocessings and the like;

[0064] (12) a memory 31 that stores therein control parameters which thecontrol parameter calculating part 30 calculates at the time of previousimage pickup (to be referred to as “previous control parameters”hereinafter) and that also stores values of previous conditionalinformation (will be described later in detail) and so on; and

[0065] (13) a correction processing part 32 that performs the variouscorrection processings on the image data by use of the controlparameters calculated anew by the control parameter calculating part 30.

[0066] The control parameter calculating part 30 receives outputs fromthe color temperature determining part 15, contrast determining part 16,color detecting part 17 and photometric sensor 18. The control parametercalculating part 30 also receives information indicative of whether theelectric flash 19 emits light or not (to be referred to as “flashinformation” hereinafter), and also receives the image pickup timesclocked by the timer 20.

[0067] The electronic camera 1 constructed as described above operatessimilarly to the conventional electronic cameras except for theoperation of the control parameter calculating part 30 and except thatcolor information is used as the control parameter for color correction.The first embodiment is characterized not by how to perform the colorcorrection but by how to calculate control parameters for achieving thevarious correction processings. For simplicity the descriptions on theoperations will be omitted except for the operation of the controlparameter calculating part 30.

[0068]FIG. 2 is a flowchart showing the operation of the controlparameter calculating part 30 in the first embodiment, and particularly,showing the operation thereof during the time when the release button ispressed down for an image pickup.

[0069] The operation of the control parameter calculating part 30 willnow be described below with reference to FIG. 2.

[0070] Each time an image pickup is performed, the control parametercalculating part 30 receives a value of the latest conditionalinformation, the flash information and the image pickup time (S1 of FIG.2).

[0071] The values of latest conditional information herein refer tovalues of the color temperature, contrast, color information andbrightness at the time of the latest image pickup. According to thepresent embodiment, the conditional information is standardized so as toadapt to the control parameters for the image pickup processings.Especially, values of the color information are calculated according tocolor differences in an angle of field, and the values are standardizedvalues 1 through 15 that correspond to the major colors within the angleof field.

[0072] On the other hand, the values of the previous conditionalinformation refer to values of the color temperature, contrast, colorinformation and brightness obtained at the time of previous imagepickup, and the control parameter calculating part 30 stores them in thememory 31 in association with image pickup times.

[0073] According to the first embodiment, values of the conditionalinformation obtained at three previous image pickups are stored in thememory 31. The flash information obtained at the previous image pickupis also stored in the memory 31.

[0074] Next, the control parameter calculating part 30 determineswhether the flash information has been varied or not (S2 of FIG. 2).Such determination can be achieved by comparing the flash informationobtained at the previous image pickup in the memory 31 with that at thelatest image pickup.

[0075] When determining that the flash information has been varied, thecontrol parameter calculating part 30 resets the previous controlparameters and the values of the previous conditional information storedin the memory 31 (S3 of FIG. 2), and determines the values of the latestconditional information (except brightness) as new control parameters(S4 of FIG. 2). Additionally, the control parameter calculating part 30stores anew the previous control parameters and the values of previousconditional information (S5 of FIG. 2).

[0076] That is, when the flash information has been varied, the controlparameter calculating part 30 recognizes the electric flash 19'schanging from ON state to OFF state or vice versa, and determines thatthe conditions of the subject have actually changed. Then, the controlparameter calculating part 30 determines the latest color temperature asthe control parameter for the white balance adjustment, the latestcontrast as the control parameter for the gray level correction, and thelatest color information as the control parameter for the colorcorrection such that the correction processing part 32 can performcorrection processings in accordance with the changes in the conditionsof the subject. Additionally, the control parameter calculating part 30stores anew the previous control parameters and the values of previousconditional information in preparation for the next image pickup.

[0077] This storing of the previous control parameters and the values ofprevious conditional information signifies that the new controlparameters are stored as previous control parameters or the values ofthe latest conditional information as values of the first previousconditional information in the memory 31. However, the values of aplurality of previous conditional information are averaged inprocessings that will be described later, and hence in the storing ofthe previous values, every set of values of the latest conditionalinformation has to be stored in the memory 31 as the values of allprevious conditional information so as to prepare for the processings.

[0078] On the other hand, when the flash information has not beenvaried, the control parameter calculating part 30 determines whether theprevious control parameters and the values of previous conditionalinformation have been reset or not (S6 of FIG. 2).

[0079] When the previous control parameters and the values of previousconditional information have been reset, the control parametercalculating part 30 determines the values of the latest conditionalinformation (except the brightness) as new control parameters (S4 ofFIG. 2) and stores anew the previous control parameters and the valuesof previous conditional information (S5 of FIG. 2).

[0080] That is, when the flash information has not been varied and theprevious control parameters and the values of previous conditionalinformation have been reset, the control parameter calculating part 30judges that for some reason (for example, because of an initializationfor shipping, an initialization associated with a set operation of thetimer 20, or the like), the previous control parameters and the valuesof previous conditional information have been reset. Then, the controlparameter calculating part 30 determines the color temperature, contrastand color information, received as the values of the latest conditionalinformation, as control parameters for the respective correctionprocessings such that the correction processing part 32 can performcorrection processings in accordance with the current conditions of thesubject. Additionally, the control parameter calculating part 30 storesanew the previous control parameters and the values of previousconditional information in preparation for the next image pickup.

[0081] On the other hand, when the previous control parameters and thevalues of previous conditional information have not been reset, thecontrol parameter calculating part 30 calculates variation values ofconditional information based on the latest values of previousconditional information (S7 of FIG. 2).

[0082] An example will be described below in which variation values ofthe color temperature, contrast, color information and brightness arecalculated as the variation values of conditional information

[0083] It should be noted that in the first embodiment the degree ofcolor information is expressed by values 1 through 15 for convenience,however, the values 1 and 15 are next to each other with regard todegrees of color. Therefore, there will be described in the following anexample where the variation value of the color information is calculatedin a slightly different manner from that in which the variation valuesof the other information are calculated.

[0084] In addition, in the example below, the times at which threeprevious images are picked up will be represented by TIME(1), TIME(2)and TIME(3), respectively, and the time at which the latest image pickupis performed will be represented by TIME(0), for simplicity. Similarly,the color temperatures obtained at the previous and latest image pickupswill be represented by PK(1), PK(2), PK(3) and PK(0), respectively; thecontrasts obtained at the previous and latest image pickups will berepresented by PCN(1), PCN(2), PCN(3) and PCN(0), respectively; thecolor information obtained at the previous and latest image pickups willbe represented by PC(1), PC(2), PC(3) and PC(0), respectively; and thebrightness obtained at the previous and latest image pickups will berepresented by PLA(1), PLA(2), PLA(3) and PLA(0), respectively.Additionally, a fixed length of time in which intervals of image pickupsare evaluated will be represented by TH.

[0085] When a Condition 1 indicated below is satisfied, the controlparameter calculating part 30 calculates the variation values of thecolor temperature, contrast, color information and brightness by use offollowing Equations 1 to 4.

TIME(0)−TIME(3)<TH  Condition 1

Variation value of colortemperature=|(PK(1)+PK(2)+PK(3))/3−PK(0)|  Equation 1

Variation value of contrast=|(PCN(1)+PCN(2)+PCN(3))/3−PCN(0)|  Equation2

Variation value of color information=(color variation value 1+colorvariation value 2+color variation value 3)/3  Equation 3

Variation value ofbrightness=|(PLA(1)+PLA(2)+PLA(3))/3−PLA(0)|  Equation 4

[0086] As to the Equation 3, the color variation values 1, 2 and 3 arecalculated by Equations 5 to 7 indicated below, and if any one of themis greater than 8, it will be converted to its complement. Thus, thevariation values of color information calculated by use of such valuesare expressed by values 0 through 8.

Color variation value 1=|(PC(1)−PC(0)|  Equation 5

Color variation value 2=|(PC(2)−PC(0)|  Equation 6

Color variation value 3=|(PC(3)−PC(0)|  Equation 7

[0087] When a Condition 2 indicated below is satisfied, the controlparameter calculating part 30 calculates the variation values of thecolor temperature, contrast, color information and brightness by use offollowing Equations 8 to 11.

TIME(0)−TIME(2)<TH  Condition 2

Variation value of color temperature=|(PK(1)+PK(2))/2−PK(0)|  Equation 8

Variation value of contrast=|(PCN(1)+PCN(2))/2−PCN(0)|  Equation 9

Variation value of color information=(color variation value 1+colorvariation value 2)/2  Equation 10

Variation value of brightness=|(PLA(1)+PLA(2))/2−PLA(0)|  Equation 11

[0088] As to the Equation 10, the color variation values 1 and 2 arecalculated by the foregoing Equations 5 and 6, and if any one of them isgreater than 8, it will be converted to its complement.

[0089] When neither of the foregoing Conditions 1 and 2 is satisfied,the control parameter calculating part 30 calculates the variationvalues of the color temperature, contrast, color information andbrightness by use of following Equations 12 to 15.

Variation value of color temperature=|PK(1)−PK(0)|  Equation 12

Variation value of contrast=|PCN(1)−PCN(0)|  Equation 13

Variation value of color information=color variation value 1  Equation14

Variation value of brightness=|PLA(1)−PLA(0)|  Equation 15

[0090] As to the Equation 14, the color variation value 1 is calculatedby the foregoing Equation 5, and if it is greater than 8, it will beconverted to its complement.

[0091] As described above, when three or more image pickups includingthe latest are performed within a certain period of time, the controlparameter calculating part 30 averages the values of previousconditional information obtained at the image pickups within the period.Then, the control parameter calculating part 30 obtains the differences(absolute values) between the averaged values and the values of thelatest conditional information as the variation values of conditionalinformation. If less than three image pickups are performed within thecertain period of time, the control parameter calculating part 30obtains the differences (absolute values) between the values of thefirst previous conditional information and the values of the latestconditional information as the variation values of conditionalinformation.

[0092] That is, if the image pickup operation is repetitively performedwithin a short period of time, the second and third previous conditionalinformation in addition to the first previous is used to calculate thevariation values of conditional information, whereby the variationvalues of conditional information can be stabilized.

[0093] Next, the control parameter calculating part 30 decides weightingrate based on both the variation values of conditional information andan elapsed period of time from the previous image pickup to the latestimage pickup (S8 of FIG. 2).

[0094] The “weighting rate” referred to herein is a rate in which theprevious control parameters and the values of the latest conditionalinformation (except the brightness) are combined. The weighting rate isdecided for every control parameter associated with the variouscorrection processings of the correction processing part 32.

[0095] That is, the weighting rate includes the following three.

[0096] (1) Color temperature weighting rate: a weighting rate of thelatest color temperature used to calculate the control parameter for thewhite balance adjustment.

[0097] (2) Contrast weighting rate: a weighting rate of the latestcontrast used to calculate the control parameter for the gray levelcorrection.

[0098] (3) Color information weighting rate: a weighting rate of thelatest color information used to calculate the control parameter for thecolor correction.

[0099] The control parameter calculating part 30 stores therein LUTs(Look Up Tables) in which the weighting rate is associated with both thevariation values of conditional information and the elapsed period oftime from the previous image pickup till the latest image pickup. Imagepickup tests are repetitively conducted to appropriately set data of theLUTs. The control parameter calculating part 30 decides the weightingrate with reference to the LUTs.

[0100]FIGS. 3, 4 and 5 are diagrams showing examples of LUTs that arereferred to when the color temperature, contrast and color informationweighting rates are decided, respectively. The LUTs are referred to inorder, starting from the top to the bottom. That is, if respectivevalues satisfy the conditions determined in the uppermost part of theLUT, for example, the weighting rate 100 will be applied, and if they donot, the second uppermost part thereof is referred to. When respectivevalues satisfy the conditions therein, weighting rate 80 will beapplied, and if they do not, the third uppermost part thereof isreferred to. In other words, a weighting rate will be selectedcorresponding to conditions which are first satisfied.

[0101] In FIGS. 3, 4 and 5, the variation values of color informationhave been standardized to values 0 through 8, as previously stated. Thevariation values of color temperature are standardized to values 0through 255. The variation values of contrast are standardized to values0 through 6. The variation values of brightness are standardized tovalues 0 through 255.

[0102] According to the LUTs of FIG. 3, 4 and 5, the color temperature,contrast and color information weighting rates, respectively, are 100percent on occasions when the variation value of brightness is large,when the elapsed time from the previous image pickup till the latestimage pickup is long, or when the variation values of conditionalinformation are greater than predetermined values. On these occasions itis highly likely that the conditions of the subject have actuallyvaried, and hence correction processing is performed preferably inaccordance with the variations in the conditions.

[0103] On the other hand, the color temperature, contrast and colorinformation weighting rates are zero percent on occasions when thebrightness varies little, when the elapsed time from the previous imagepickup till the latest image pickup is very short, or when the variationvalues of conditional information are very small. On these occasions itis highly likely that the same subject is being continuously imaged, andhence correction processing of high stability is preferably performed.

[0104] In intermediate situations between the above two cases, thevariation value of the brightness, the elapsed period of time from theprevious image pickup till the latest image pickup, and the variationvalues of all conditional information are evaluated in steps. Accordingto the evaluation result, the brightness weighting rate, contrastweighting rate, and color information weighting rate will be within arange between 20 and 80 percent (both inclusive).

[0105] Next, the control parameter calculating part 30 combines theprevious control parameters and the values of the latest conditionalinformation (except the brightness) according to the weighting ratesdecided as described above, thereby calculating new control parameters(S9 of FIG. 2).

[0106] That is, when the weighting rates of the color temperature,contrast and color information are 100 percent, the color temperature,contrast and color information obtained as the values of the latestconditional information are determined as new control parameters. On theother hand, when the weighting rates of the color temperature, contrastand color information are zero percent, the previous control parametersare determined as new control parameters.

[0107] When the weighting rates of the color temperature, contrast andcolor information are between 20 and 80 percent (both inclusive), thecolor temperature, contrast and color information obtained as the valuesof the latest conditional information are properly combined with theprevious control parameters, thereby calculating new control parameters.

[0108] Then, the control parameter calculating part 30 prepares for anext image pickup, updating the previous control parameters and thevalues of previous conditional information (S10 of FIG. 2). That is, thecontrol parameter calculating part 30 determines the previous controlparameters as the new control parameters, and updates the values ofprevious conditional information such that the first previousconditional information become the second previous, the second becomethe third previous, the latest conditional information become the firstprevious.

[0109] As described above, according to the first embodiment, the newcontrol parameters, which are used in the correction processings on theimage data produced at the latest image pickup, are calculated bycombining the previous control parameters with the values of the latestconditional information in accordance with the variation values ofconditional information. The weighting rates decided as described aboveare used for the combining, such that the higher the necessity ofperforming correction processings in accordance with conditionalvariations, the higher the weighting rate of the latest conditionalinformation, and the higher the necessity of performing stablecorrection processings, the higher the weighting rate of previouscontrol parameters. Thus, the correction processings according to thefirst embodiment are performed with adaptability or stability dependingon actual conditions.

[0110] Also according to the first embodiment, when the flashinformation has been varied, it is judged that the conditions of thesubject have remarkably varied. In such a case, the values of the latestconditional information are used to calculate new control parameters,and the previous control parameters and the values of previousconditional information are reset. Thus, the values of previousconditional information prior to a variation in the flash information donot affect the control parameters to be calculated at the next imagepickup. As a result, even when images are picked up with flash, thecorrection processings performed are with adaptability or stabilitydepending on the conditions.

SECOND EMBODIMENT

[0111] A second embodiment of the present invention will now bedescribed below.

[0112] The second embodiment is characterized by control parameters tobe used for an exposure control which is performed in the image pickuppart of an electronic camera when the release button is pressed down,and by the calculation of control parameters to be used for a variety ofcorrection processings on digitized image data (e.g., white balanceadjustment, gray level correction, color correction and so on). In theelectronic camera 1 constructed as shown in FIG. 1, the controlparameter calculating part 30 calculates such control parameters.

[0113] Then, parts of the second embodiment that are different from thefirst embodiment will now be described by use of the same referencelabels as are shown in FIG. 1.

[0114] In the electronic camera 1, the control parameter calculatingpart 30 repetitively calculates control parameters at predetermined timeintervals regardless of whether or not the release button is presseddown. The color temperature determining part 15, contrast determiningpart 16, color detecting part 17 and photometric sensor 18 repetitivelydetermine the color temperature, contrast, color information andbrightness in association with the calculations of the controlparameters. Then, when the release button is pressed down, the imagepickup part 11 performs an exposure control using the latest controlparameters calculated immediately before the press-down. Similarly, thecorrection processing part 32 performs the various correctionprocessings using the latest control parameters calculated immediatelybefore the press-down.

[0115] In the second embodiment, the memory 31 stores therein, as valuesof previous conditional information, three previous determinationresults from the color temperature determining part 15, contrastdetermining part 16, color detecting part 17 and photometric sensor 18.The values of brightness which the photometric sensor 18 determines arestandardized to values suitable for control parameters to be used forthe exposure control.

[0116]FIG. 6 is a flowchart showing the operation of the controlparameter calculating part 30 according to the second embodiment.

[0117] The operation of the control parameter calculating part 30 willnow be described below with reference to FIG. 6.

[0118] The control parameter calculating part 30 repetitively determineswhether a prescribed time (e.g., one second through two seconds) haselapsed or not (S1 of FIG. 6), and waits until the prescribed timeelapses.

[0119] When the prescribed time has elapsed, the control parametercalculating part 30 obtains the values of the latest conditionalinformation (S2 of FIG. 6). The control parameter calculating part 30calculates the variation values of conditional information from thevalues of the latest and previous conditional information (S3 of FIG.6). That is, the control parameter calculating part 30 averages thevalues of three previous conditional information stored in the memory31, and then determines, as the variation values of conditionalinformation, the absolute values of the differences between theresultant average values and the values of the latest conditionalinformation.

[0120] Next, the control parameter calculating part 30 decides theweighting rates from both the variation values of conditionalinformation and the elapsed time from the first previous image pickuptime (S4 of FIG. 6).

[0121] The weighting rates include the color temperature, contrast,color information and brightness. The brightness weighting rate is aweighting rate of the latest brightness to be used at the calculation ofthe control parameters for an exposure control.

[0122]FIG. 7 is a diagram showing an example of the LUT to be referredto at the decision of the above brightness weighting rate.

[0123] The variation values in FIG. 7 are standardized similarly tothose in FIGS. 3, 4 and 5.

[0124] According to the LUT of FIG. 7, the brightness weighting rate is100 percent on occasions when the variation value of brightness islarge, when the elapsed time from the previous to the latest imagepickup is long, or when the variation values of conditional informationare greater than predetermined values. On such occasion, it is verylikely that the conditions of the subject have actually varied.

[0125] On the other hand, the brightness weighting rate is zero percenton occasions when the brightness varies little, when the elapsed timefrom the previous to the latest image pickup is very short, when thevariation values of conditional information are very small. On suchoccasion, it is very likely that the same subject is being continuouslyimaged.

[0126] In intermediate conditions between the above two cases, thevariation value of the brightness, the elapsed period of time from theprevious image pickup till the latest image pickup, and the variationvalues of all conditional information are evaluated in steps. Accordingto such evaluation results, the weighting rates of the colortemperature, contrast and color information will be within a rangebetween 20 and 80 percent (both inclusive).

[0127] Next, the control parameter calculating part 30 combines theprevious control parameters and the values of the latest conditionalinformation according to the weighting rates decided as described above,thereby calculating new control parameters (S5 of FIG. 6).

[0128] That is, when the weighting rate is 100 percent, the values ofthe latest conditional information are determined as the new controlparameters. When the weighting rate is zero percent, the previouscontrol parameters are determined as the new control parameters. Whenthe weighting rate is between 20 and 80 percent (both inclusive), thevalues of the latest conditional information are properly combined withthe previous control parameters, thereby calculating the new controlparameters.

[0129] Then, the control parameter calculating part 30 updates theprevious control parameters and the values of previous conditionalinformation (S6 of FIG. 6). After this updating, the control parametercalculating part 30 repeats the processings of the steps S1 through S6of FIG. 6.

[0130] According to the second embodiment as described above, thecontrol parameters to be used for the exposure control and for thecorrection processings are repetitively calculated for preparation for anext image pickup. It should be noted that such control parameters arecalculated by combining the previous control parameters and the valuesof the latest conditional information in accordance with the variationvalues of conditional information. In such combination, similarly to thefirst embodiment, the weighting rates are used such that the higher thenecessity of performing correction processings in accordance withconditional variations, the higher the weighting rate of the latestconditional information, and the higher the necessity of performingstable correction processings, the higher the weighting rate of previouscontrol parameters. Thus, the exposure control and the correctionprocessings according to the second embodiment are performed withadaptability or stability depending on actual conditions.

[0131] The invention is not limited to the above embodiments and variousmodifications may be made without departing from the spirit and scope ofthe invention. Any improvement may be made in part or all of thecomponents.

What is claimed is:
 1. An electronic camera comprising: an imaging partfor imaging a subject to produce image data; a conditional informationdetermining part for determining conditional information, theconditional information being indicative of a condition of the subjectat a time when said imaging part produces said image data; a storagepart for storing previous conditional information determined by saidconditional information determining part; and a correction processingpart for performing correction processing on said image data, accordingto both the previous conditional information stored in said storage partand current conditional information which is determined by saidconditional information determining part when said imaging part producessaid image data.
 2. The electronic camera according to claim 1, whereinsaid conditional information determining part; determines at least acolor temperature of the subject as said conditional information whensaid correction processing part performs a white balance adjustment or acolor correction; determines at least a contrast of the subject as saidconditional information when said correction processing part performs agray level correction; and generates color information when saidcorrection processing part performs a color correction, the colorinformation being quantitatively indicative of a major color in an angleof field.
 3. The electronic camera according to claim 1, wherein: saidcorrection processing part has a control parameter calculating part thatcalculates a control parameter every time said imaging part producessaid image data, the control parameter being used for the correctionprocessing on the image data; said storage part stores a previouscontrol parameter calculated by said control parameter calculating part;and said control parameter calculating part calculates a new controlparameter in accordance with a difference between the previous andcurrent conditional information by combining the previous conditionalinformation with the control parameter obtained according to the currentconditional information.
 4. The electronic camera according to claim 3,wherein: said conditional information includes brightness of thesubject; when a variation amount of the brightness is equal to orgreater than an upper limit value, said control parameter calculatingpart determines the control parameter obtained according to the currentconditional information as the new control parameter; and when thevariation amount of the brightness is less than a lower limit value,said control parameter calculating part determines the previous controlparameter as the new control parameter.
 5. The electronic cameraaccording to claim 1, further comprising an image pickup time obtainingpart for obtaining image pickup time every time said imaging partproduces image data, wherein said correction processing part has acontrol parameter calculating part that calculates a control parameterevery time said imaging part produces said image data, the controlparameter being used for the correction processing on the image data;said storage part stores a previous control parameter calculated by saidcontrol parameter calculating part; when an elapsed length of time fromprevious image pickup time to present image pickup time is equal to orgreater than an upper limit value, said control parameter calculatingpart determines the control parameter calculated according to thecurrent conditional information as the new control parameter; and whenthe elapsed length of time is less than a lower limit value, saidcontrol parameter calculating part determines the previous controlparameter stored in said storage part as the new control parameter. 6.The electronic camera according to claim 1, further comprising anelectric flash for emitting light, wherein: said correction processingpart has a control parameter calculating part that calculates a controlparameter every time said imaging part produces said image data, thecontrol parameter being used for the correction processing on the imagedata; said storage part stores a previous control parameter calculatedby said control parameter calculating part; and when presence or absenceof the emitting from said electric flash changes between a previousimage pickup and a present image pickup, said control parametercalculating part determines the control parameter obtained according tothe current conditional information as the new control parameter; andwhen presence or absence of the emitting from said electric flash doesnot change between the previous image pickup and the present imagepickup, said control parameter calculating part determines the previouscontrol parameter stored in said storage part as the new controlparameter.
 7. The electronic camera according to claim 6, wherein: whenpresence or absence of the emitting from said electric flash changesbetween the previous image pickup and the present image pickup, saidcontrol parameter calculating part initializes the previous controlparameter and the previous conditional information stored in saidstorage part.
 8. An electronic camera comprising: an imaging part forimaging a subject to produce image data; a conditional informationdetermining part for repetitively determining conditional informationwhich is indicative of a condition of the subject; a storage part forstoring previous conditional information determined by said conditionalinformation determining part; and a control parameter calculating partfor repetitively calculating a control parameter according to both theprevious conditional information stored in said storage part and currentconditional information determined by said conditional informationdetermining part, the control parameter being used for an exposurecontrol at a time when said imaging part produces the image data; and anexposure control part for performing the exposure control by use of thecontrol parameter which is calculated immediately before said imagingpart produces the image data.
 9. An electronic camera comprising: animaging part for imaging a subject to produce image data; a conditionalinformation determining part for repetitively determining conditionalinformation which is indicative of a condition of the subject; a storagepart for storing previous conditional information determined by saidconditional information determining part; a control parametercalculating part for repetitively calculating a control parameteraccording to both the previous conditional information stored in saidstorage part and current conditional information determined by saidconditional information determining part, the control parameter beingused for correction processing on the image data produced by saidimaging part; and a correction processing part for performing thecorrection processing by use of the control parameter calculatedimmediately before said imaging part produces the image data.
 10. Theelectronic camera according to claim 9, wherein said conditionalinformation determining part: determines at least a color temperature ofthe subject as said conditional information when said correctionprocessing part performs a white balance adjustment or a colorcorrection; determines at least a contrast of the subject as saidconditional information when said correction processing part performs agray level correction; and generates color information when saidcorrection processing part performs a color correction, the colorinformation being quantitatively indicative of a major color within anangle of field.
 11. The electronic camera according to claim 8, wherein:said storage part stores a previous control parameter calculated by saidcontrol parameter calculating part; and said control parametercalculating part calculates a new control parameter in accordance with adifference between the previous and current conditional information bycombining the previous conditional information with the controlparameter calculated according to the current conditional information.12. The electronic camera according to claim 11, wherein: saidconditional information includes brightness of the subject; when avariation amount of the brightness is equal to or greater than an upperlimit value, said control parameter calculating part determines thecontrol parameter obtained according to the current conditionalinformation as the new control parameter; and when the variation amountof the brightness is less than a lower limit value, said controlparameter calculating part determines the previous control parameter asthe new control parameter.
 13. The electronic camera according to claim8, further comprising image pickup time obtaining part for obtainingimage pickup time every time said imaging part produces image data,wherein said storage part stores a previous control parameter calculatedby said control parameter calculating part; when an elapsed length oftime from previous image pickup time to present image pickup time isequal to or greater than an upper limit value, said control parametercalculating part determines the control parameter calculated accordingto the current conditional information as the new control parameter; andwhen the elapsed length of time is less than a lower limit value, saidcontrol parameter calculating part determines the previous controlparameter stored in said storage part as the new control parameter.